Pen



FIG. 1 is an upper front right perspective view of a pen showing my new design;

FIG. 2 is a right side elevation view thereof;

FIG. 3 is an enlarged top plan view thereof;

FIG. 4 is a front elevation view thereof;

FIG. 5 is a left side elevation view thereof;

FIG. 6 is a bottom plan view thereof; and,

FIG. 7 is a rear elevation view thereof.

The broken lines showing portions of the top are included for the purpose of illustrating environment and form no part of the claimed design. 

The ornamental design for a pen, as shown and described. 